threadpool.h

#ifndef THREADPOOL_H
#define THREADPOOL_H

#include <iostream>
#include <future>
#include <vector>
#include <queue>
#include <thread>
#include <functional>
#include <condition_variable>
#include <mutex>

class ThreadPool
{
private:
    std::vector<std::thread> workers;
    std::queue<std::function<void()>> tasks;
    std::mutex queue_mutex;
    std::condition_variable condition;
    bool stop;

public:
    ThreadPool(size_t threads) : stop(false)
    {
        for (size_t i = 0; i < threads; ++i)
        {
            workers.emplace_back([this]
                                 {
                while (true) {
                    std::function<void()> task;
                    {
                        std::unique_lock<std::mutex> lock(this->queue_mutex);
                        this->condition.wait(lock, [this] {
                            return this->stop || !this->tasks.empty();
                        });
                        if (this->stop && this->tasks.empty()) {
                            return;
                        }
                        task = std::move(this->tasks.front());
                        this->tasks.pop();
                    }
                    task();
                } });
        }
    }

    template <class F>
    auto enqueue(F &&f) -> std::future<decltype(f())>
    {
        using return_type = decltype(f());
        auto task = std::make_shared<std::packaged_task<return_type()>>(std::forward<F>(f));
        std::future<return_type> res = task->get_future();
        {
            std::unique_lock<std::mutex> lock(queue_mutex);
            tasks.emplace([task]()
                          { (*task)(); });
        }
        condition.notify_one();
        return res;
    }

    ~ThreadPool()
    {
        {
            std::unique_lock<std::mutex> lock(queue_mutex);
            stop = true;
        }
        condition.notify_all();
        for (std::thread &worker : workers)
        {
            worker.join();
        }
    }
};
#endif